Raisman, who previously said Nassar abused her, told CNN that conversation occurred in 2011, five years before Nassar was exposed.
Neither Geddert nor his attorney, Cameron Getto, could immediately be reached to comment.
Geddert, who worked with Nassar at his Lansing, Michigan-area gymnastics centre Twistars, was suspended in January by USA Gymnastics (USAG), the sport's governing body, and subsequently retired.
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The Eaton County Sheriff's Office in Michigan on Tuesday said it was investigating complaints against Geddert, but did not provide further details.
A lawsuit filed against Nassar, Michigan State, where Nassar also worked, USAG and Twistars asserted Geddert was made aware of allegations against the doctor as early as 1998 but took no action.
In court filings in the case, Geddert's lawyer has said he did not witness the abuse and only learned of it after Nassar was arrested.
"Just like everyone else, Mr. Geddert was at first incredulous when these accusations came to light only to ultimately realise that the allegations against Nassar were indeed true," Geddert's attorney wrote in court documents. "Mr. Geddert was simply one individual in an extraordinarily long line of people who were duped."
Nassar was given two prison sentences in Michigan of 40 to 125 years and 40 to 175 years for molesting young female gymnasts. He is also serving a 60-year federal term for child pornography convictions.
Many of Nassar's victims, during his sentencing hearings, criticized Geddert for creating a hostile environment at his gym and turning a blind eye to Nassar's abuse. Geddert ran Twistars, where athletes said Nassar molested them in a back room.
The case against Nassar has sparked investigations into how U.S. Olympic Committee officials, USAG and Michigan State, failed to investigate complaints about him.
The USA Gymnastics board resigned in the fallout from the Nassar scandal and the president of Michigan State University resigned after facing criticism for not doing enough to stop the abuse by the doctor.
(Reporting by Ben Klayman in Detroit, additional reporting by Joseph Ax in New York; Editing by Tom Brown)
